1. Field of the Invention
The present invention relates generally to sealing of mechanical penetrations in a roofing membrane, and more specifically, to a pipe curb accessory for single ply roofing membranes covering a roof deck.
2. Prior Art
A roofing system generally includes a roof deck which is considered the structural supporting surface of a building extending between the surrounding exterior walls of the building. The roof deck may be constructed from plywood, metal decking or concrete or any other suitable material. Depending upon the construction, the roof deck may extend over the surrounding exterior walls or the roof deck may stop short of the exterior walls thereby forming a parapet wall, i.e., a low retaining wall at the edge of the roof deck. If desired, the roofing system may also include an insulation barrier formed from polyisocyanarate or any other suitable material applied over the roof deck.
To make the roof deck and building weather resistant a single-ply membrane roof is installed over the roof deck. The single-ply membrane roof refers to a water impermeable single sheet of polymeric material such as ethylene propylene diene rubber (EPDM) having a preapplied hot melt adhesive, chlorinated polyethylene, polyvinyl chloride, or chlorosulfanated polyethylene. The membrane roof has heretofore been installed on the roof deck using a variety of different methods.
In a typical low slope, single-ply membrane roof, provision must be made for sealing penetrations of the roof by vent pipes, support straps, conduits, guy anchors and similar elements. Generally, a pitch pocket or pan (a flanged, open bottomed enclosure made of sheet metal or other material, placed around a penetration through the roof, filled with grout and bituminous or polymeric sealants to seal the area around the penetration), which surrounds the penetrating element is used. A sealant is poured into the pan around the penetrating element. Various types of pitch pockets or pans have been proposed. Examples may be found in U.S. Pat. No. 3,838,544 entitled Adjustable Pitch Pocket Structure, which issued on Oct. 1, 1974, to Hindall; U.S. Pat. No. 4,928,443 entitled Pourable Sealer Pocket, which issued on May 29, 1990, to Goodman et al.; U.S. Pat. No. 4,934,117 entitled Pitch Pocket and Method of Forming Same, which issued on Jun. 19, 1990, to Barksdale; U.S. Pat. No. 4,937,991 entitled Flashing Unit for Sealing Roof Penetrations, which issued on Jul. 3, 1990, to Orth; U.S. Pat. No. 5,493,827 entitled Pitch Pocket, which issued on Feb. 27, 1996, to Georgeau et al; and U.S. Pat. No. 5,768,838 entitled Polyurethane Pitch Pocket, which issued on Jun. 23, 1998 to Georgeau et al.
In one approach, a prefabricated angle iron flange, at least two inches deep, is fabricated away from the job site. The flange is bonded to the roofing membrane with a solvent-based contact cement, thus forming a metal dam around the roof penetration. Sheet rubber flashing is applied to the outer surfaces of the flange with contact cement to prevent rusting and corrosion. The perimeter of the applied rubber flashing is then sealed with a bead of solvent-based rubber caulking to keep it from being underridden by water. A two-part urethane rubber pourable sealant is mixed and poured into the cavity until it is level with the top of the metal flange. The liquid rubber cures to form a solid rubber seal around the roof penetration.
However, the rubber seal over time often was penetrated by water because it was not properly applied or because over time the seal gave way. Further, the installation of available pitch pans is time consuming, complicated and expensive. The process generally takes about forty five minutes per unit and is labor intensive. The complexity of the procedure under field conditions has caused errors in workmanship and improper installations, leading to failure of the seal formed by the pitch pan. Because of the time and expense associated with traditional pitch pans, many contractors have compensated by filling the pan cavity with sand, mortar or urethane foam and covering the top surface with caulk to give the appearance of a solid rubber seal. These practices have lead to frequent leaks and failures that make traditional pitch pans unreliable.
Therefore, a need exists for a leak proof system for single ply roofing membranes which simplifies field application, which reduces the cost of materials and which provides for a more reliable waterproof seal between a roof membrane and penetration therein.